1. Field of the Invention
The invention relates to a method and an apparatus for copying photographic originals onto single-sheet copy material.
2. State of the Art
Numerous methods of photographic copying using printers are known. In a frequent application, the frames of a negative film are copied onto photo paper. In terms of the equipment, a fundamental distinction is made between so-called high-speed printers (or high-speed lines) which produce only the most frequently used sizes of paper prints in very large numbers, and so-called minilabs whose primary field of application is the production of particular sizes of paper prints. Minilabs are also suitable for smaller or medium numbers of formats that occur quite often.
In professional photography, the formats or sizes desired are often variable, so that it is not expedient in practice to use minilabs to process striplike copy material (i.e. photo paper that comes on rolls). When minilabs are used, single-sheet copy material is typically used, i.e., photo paper in individual sheets. The individual sheets correspond in their dimensions to the desired format of the paper print. Since, as a rule, the negatives all have the same dimensions, the scale of projection is altered in the enlargement operation to achieve the desired size of paper print.
In a minilab, the negative to be copied is scanned (with a scanner) and the requisite quantities of copying light are ascertained with the aid of the scanning values obtained. Once the requisite quantities of copying light have been ascertained, the negative to be copied is guided on a film stage into the exposure beam path, and the requisite projection scale is adjusted. At the same time, the unexposed sheet of photo paper of the desired format is transported on a paper stage, also into the exposure beam path. This operation is performed without exposing the photo paper to copying light (for example, the light of the copying lamp is blocked with a baffle). If the negative to be copied and the sheet of photo paper have reached the appropriate copying position, the blocking unit is removed and the negative is copied onto the photo paper using the previously ascertained quantities of copying light. Next, the light coming from the copying lamp is blocked again, and the exposed photo paper is removed from the paper stage and processed further.
The operation described above is such that a sheet of photo paper is transported on the paper stage, (i.e., exposing stage) the negative is copied onto the photo paper and then the exposed photo paper is removed from the paper stage. Once this operation is concluded, the next sheet of photo paper is transported onto the paper stage, the corresponding negative is copied and the exposed photo paper is removed from the paper stage, and so forth. Only one sheet of paper is thus ever located on the paper stage at any given time. In a printer intended for producing copies of only a small number of formats, and in which the paper stage is well utilized even with the small formats, this kind of procedure is acceptable. However, if a great many different formats are to be processed, the utilization of the paper stage, especially for the small formats, is quite poor. At the same time, the small formats do occur with a certain frequency and thus the efficiency of the equipment is in need of improvement.